1. Field of the Invention
The invention relates to a lens barrel including a structure that prevents backlash in engagement of a cam groove and a cam follower.
2. Description of the Related Art
Conventionally, an image pickup apparatus that picks up an image of an object is generally in a form in which a lens barrel, which is configured by having an image pickup optical system for forming an optical image of the object to be a target of image pickup, inside the lens barrel, is placed integrally with or attachably and detachably from an apparatus main body.
A lens barrel that is applied to the conventional image pickup apparatus is configured by including a plurality of optical lenses for configuring an image pickup optical system, a plurality of lens holding members that respectively hold the plurality of optical lenses and are formed into barrel shapes or frame shapes, a barrel member for driving and a drive source that are for causing a predetermined lens holding member of the plurality of lens holding members to perform advance and retreat movement in a direction along an optical axis, a drive mechanism that transmits a drive force of the drive source and the like.
The lens barrel which is disclosed by Japanese Patent Application Laid-Open Publication No. 11-174305, for example, has a cam barrel (a barrel member for driving) in which a cam groove is formed, and a lens holding barrel (a lens holding member) that includes a cam pin that performs cam coupling to the cam groove of the cam barrel, and holds some optical lenses of an image pickup optical system. The cam barrel rotates by receiving the drive force from the drive source, and thereby the cam pin moves in the cam groove, whereby the lens holding barrel is configured to move in a direction along the optical axis.
In the above case, a configuration is adopted, in which the cam grooves and the cam pins which are paired are placed at three spots substantially equidistantly in circumferential directions of the respective barrel members (the cam barrel and the lens holding barrel). Accordingly, the lens holding barrel is in a state in which the lens holding barrel is supported at the three spots that are the sites where the cam pins and the cam grooves perform cam coupling and is capable of performing advance and retreat movement, with respect to the cam barrel.